To be or not to be a hamlet pair in sympatry

Salzburger, Walter

doi:10.1111/j.1365-294x.2008.03711.x

Cited by 7 publications

(5 citation statements)

References 15 publications

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“…This could be due to external factors that mask the effect of AF(G)P emergence in non-notothenioid taxa. Most adaptive radiations occur in geographically confined areas, a potential prerequisite [51] that is satisfied for Antarctic continental shelves, but less so for Arctic habitats. In addition, dispersal of zoarcids to Antarctica in the Miocene [49], when the notothenioid diversification had already filled most available niche space, could have limited their radiation.…”

Section: Discussionmentioning

confidence: 99%

On the Origin and Trigger of the Notothenioid Adaptive Radiation

Matschiner¹,

Hanel²,

Salzburger³

2011

PLoS ONE

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Adaptive radiation is usually triggered by ecological opportunity, arising through (i) the colonization of a new habitat by its progenitor; (ii) the extinction of competitors; or (iii) the emergence of an evolutionary key innovation in the ancestral lineage. Support for the key innovation hypothesis is scarce, however, even in textbook examples of adaptive radiation. Antifreeze glycoproteins (AFGPs) have been proposed as putative key innovation for the adaptive radiation of notothenioid fishes in the ice-cold waters of Antarctica. A crucial prerequisite for this assumption is the concurrence of the notothenioid radiation with the onset of Antarctic sea ice conditions. Here, we use a fossil-calibrated multi-marker phylogeny of nothothenioid and related acanthomorph fishes to date AFGP emergence and the notothenioid radiation. All time-constraints are cross-validated to assess their reliability resulting in six powerful calibration points. We find that the notothenioid radiation began near the Oligocene-Miocene transition, which coincides with the increasing presence of Antarctic sea ice. Divergence dates of notothenioids are thus consistent with the key innovation hypothesis of AFGP. Early notothenioid divergences are furthermore congruent with vicariant speciation and the breakup of Gondwana.

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Section: Discussionmentioning

confidence: 99%

On the Origin and Trigger of the Notothenioid Adaptive Radiation

Matschiner¹,

Hanel²,

Salzburger³

2011

PLoS ONE

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119

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“…The species flocks of cichlid fishes in the East African Great Lakes undoubtedly constitute the most diverse extant vertebrate adaptive radiations (Seehausen 2006). Like all other famous cases, these radiations have occurred in habitats with island‐like properties: large freshwater lakes that, from the fishes’ point of view, are what an island is for terrestrial animals (Salzburger 2008). Lakes Tanganyika, Malawi, and Victoria are each teeming with a unique set of hundreds of endemic cichlid species, which are likely to have evolved — together with plenty of species in rivers and smaller lakes — in the last few millions to several thousands of years only (Seehausen 2002; Verheyen et al .…”

Section: The Adaptive Radiations Of Cichlid Fishes mentioning

confidence: 98%

The interaction of sexually and naturally selected traits in the adaptive radiations of cichlid fishes

2009

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The question of how genetic variation translates into organismal diversity has puzzled biologists for decades. Despite recent advances in evolutionary and developmental genetics, the mechanisms that underlie adaptation, diversification and evolutionary innovation remain largely unknown. The exceptionally diverse species flocks of cichlid fishes are textbook examples of adaptive radiation and explosive speciation and emerge as powerful model systems to study the genetic basis of animal diversification. East Africa's hundreds of endemic cichlid species are akin to a natural mutagenesis screen and differ greatly not only in ecologically relevant (hence naturally selected) characters such as mouth morphology and body shape, but also in sexually selected traits such as coloration. One of the most fascinating aspects of cichlid evolution is the frequent occurrence of evolutionary parallelisms, which has led to the question whether selection alone is sufficient to produce these parallel morphologies, or whether a developmental or genetic bias has influenced the direction of diversification. Here, I review fitness-relevant traits that could be responsible for the cichlids' evolutionary success and assess whether these were shaped by sexual or natural selection. I then focus on the interaction and the relative importance of sexual vs. natural selection in cichlid evolution. Finally, I discuss what is currently known about the genes underlying the morphogenesis of adaptively relevant traits and highlight the importance of the forthcoming cichlid genomes in the quest of the genetic basis of diversification in this group.Keywords: adaptive evolution, evo-devo, evolutionary genomics, explosive speciation, organismal diversification, parallel evolution And what is the molecular basis of adaptation, evolutionary innovation and diversification? A key to these and related questions is the comparative study of exceptionally diverse yet relatively young species assemblages that have radiated in geographically well-defined areas. This strategy is anything but novel and dates back to the dawn of evolutionary research, with the fringillid finches of the Galapagos archipelago being the primary and most prominent case. These 14 songbird species -commonly referred to as Darwin's finches in honour of their discoverer -make up the classic example of adaptive radiation, i.e. the rapid proliferation of an ecologically and morphologically differentiated species assemblage from a single ancestor as a consequence of adaptation to divergent environments (Simpson 1953;Schluter 2000 The actual number of cichlid species in East Africa's Great Lakes is undetermined and, at least in the cases of Victoria and Malawi, a matter of debate. About 250 cichlid species are known to occur in Lake Tanganyika. Higher estimates for Lake Malawi range around 700-800 species (Snoeks 2001;Turner et al. 2001), making its fauna the most species-rich species flock known. The situation is less clear for the cichlid assemblage of Lake Victoria for two reasons. ...

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“…In fishes, most studies on adaptive radiation focus on freshwater systems, with the cichlid species flocks of the East African Great Lakes being the prime examples (Salzburger 2008, 2009). The Antarctic notothenioids represent a marine species flock that evolved under extreme environmental conditions (Eastman & Clarke 1998; Eastman 2000).…”

Section: Introductionmentioning

confidence: 99%

Parallel ecological diversification in Antarctic notothenioid fishes as evidence for adaptive radiation

et al. 2011

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Antarctic notothenioid fishes represent a rare example of a marine species flock. They evolved special adaptations to the extreme environment of the Southern Ocean including antifreeze glycoproteins. Although lacking a swim bladder, notothenioids have diversified from their benthic ancestor into a wide array of water column niches, such as epibenthic, semipelagic, cryopelagic and pelagic habitats. Applying stable carbon (C) and nitrogen (N) isotope analyses to gain information on feeding ecology and foraging habitats, we tested whether ecological diversification along the benthic-pelagic axis followed a single directional trend in notothenioids, or whether it evolved independently in several lineages. Population samples of 25 different notothenioid species were collected around the Antarctic Peninsula, the South Orkneys and the South Sandwich Islands. The C and N stable isotope signatures span a broad range (mean δ(13) C and δ(15) N values between -25.4‰ and -21.9‰ and between 8.5‰ and 13.8‰, respectively), and pairwise niche overlap between four notothenioid families was highly significant. Analysis of isotopic disparity-through-time on the basis of Bayesian inference and maximum-likelihood phylogenies, performed on a concatenated mitochondrial (cyt b) and nuclear gene (myh6, Ptr and tbr1) data set (3148 bp), showed that ecological diversification into overlapping feeding niches has occurred multiple times in parallel in different notothenioid families. This convergent diversification in habitat and trophic ecology is a sign of interspecific competition and characteristic for adaptive radiations.

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To be or not to be a hamlet pair in sympatry

Cited by 7 publications

References 15 publications

On the Origin and Trigger of the Notothenioid Adaptive Radiation

On the Origin and Trigger of the Notothenioid Adaptive Radiation

The interaction of sexually and naturally selected traits in the adaptive radiations of cichlid fishes

Parallel ecological diversification in Antarctic notothenioid fishes as evidence for adaptive radiation

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